This is a spectacular failure.  The force involved must have been tremendous.  It took a lot to bend that balance shaft.  I wouldn't use that crank assembly; the rod really took a hit.  I imagine the rod bearing is brinelled, and the bore in the rod is most likely out of round.  The crank assembly is most likely twisted and/or spread.  At least do runout checks.

Can you remove the main bearing and get a look at the drive pin in the drive gear?

Could you possibly take some pictures of the driven gear fracture?  A few shots that look directly at the granular surface of the fracture.  Straight at the fracture like the arrows show.

Broken piece one

The replacement bottom end is in the mail to you and is scheduled to arrive on Monday.

DBM, I looked up Brinelled and still don't understand what you are getting at.

Celeste, thanks so much for posting the photos of the broken gear.  I wanted to see if there was any evidence of crack propagation.   If this was a fatigue failure, there should be evidence of crack propagation and wear in the fine tissues of the break.  There are a few areas that might be evidence of crack propagation and/or wear, but I am not a metallurgist or materials engineer.  It would have to be examined with magnification by an expert.

I have seen many fractures that were caused by fatigue where the surfaces exhibited wear and rounded edges.  The cracks start in a corner or stress riser and propagate rather slowly at first.  As the component is subjected to cyclic loads, the crack continues to propagate, which reduces the cross section of the area subjected to the load.  The reduction in area results in more stress which accelerates the rate of propagation.  The area that has already cracked wears as the part is continually subjected to the cyclic load.  Many times, the edges become rounded, probably due to chipping.

I really can't tell from your pictures, but there are a few suspect areas.  For instance, the areas circled in yellow could be indications of propagation and wear.

You can see from your photo of the bearing, that it was probably a clean break.  That would be consistent with a bearing that was subjected to that heavy shaft being bent almost instantaneously.  I've seen a lot of failed ball bearings, but have never seen one with an inner race that broke off.

Clean break, snap.

I am very concerned about these balancer failures.  Imagine how things could have gone if Celeste was rippin down the freeway at 70 mph....or worse yet....trying to break the LSR.  That balance shaft packs a ton of energy.  Smacking it with a connecting rod and having the whole shiteree go flyin out the front of the engine could be physically painful.  That's why I keep asking questions and requesting photos.  I want to understand this failure because I'm selfish.  I want to keep my skin attached, and kiss my wife at the end of each ride.

If these are random failures that simply occur for no reason, then I don't wanna be riding an LS650.  On the other hand, if these are failures that can be explained, like the drive pin workin loose because there's no pinch on the gear, then it's a manageable condition.  Never overtighten the primary nut.  Inspect the cam drive sprocket periodically.  Check the drive pin with a gage every time the cylinder is removed.  Etc., etc., etc.....

Celeste, please, can you remove that main bearing and inspect the drive gear.  Is the pin in the gear or not?  I know you previously stated that the pin is missing, but I get the feeling that you said that because you didn't see the pin sticking out of the crank.  When things are correct, that pin doesn't stick out.  It should be situated a little less than 1/2" in the hole.  

If the pin is missing, we need to figure out why.  Was the primary nut loose during this particular failure?  Was the primary nut loose for an extended period during some prior operating period?  During prior operation, was the engine operated for an extended period of time with a fractured cam drive sprocket?

I think operating with insufficient pinch on that balancer drive gear allows the cyclic loading to work the drive pin loose.  Suzuki should have made this thing with a step in the bore in the crank.  That way, even if the pin works loose, it can't disengage and fall out.

Celeste, if your drive pin is still in there, then we need to focus on other possibilities.  Somehow, the balancer timing got thrown off.  That could be due to a key failure (driven gear), cushion spring stops missing, balancer timing incorrect to begin with (seems very unlikely), fatigue failure of the driven gear, catastrophic failure of a balancer bearing.  

Any other ideas?